We’ve all seen that comment spam is becoming a serious problem. Particularly on Movable Type weblogs, where the generated pages are all very similar in structure and semantics, spammers are abusing comment systems to increase their rank on Google.

Even more frustrating than the spamming problem is the fact that there isn’t a simple solution that will work for everyone and that all options have their own sets of pros and cons. During the past couple of months, we’ve been throwing around ideas at Six Apart about the best ways to combat spammers.

Readers of your weblog must register before posting to your weblog.
Before someone can post a comment to your weblog, they must register with your site.

For many webloggers, this solution is not ideal. Informal polling of webloggers has revealed that many do not want to require someone to register before posting. It usually discourages conversations from forming and is a barrier for open discussion. Additionally, without federation, logins on multiple weblogs become unmanageable.

While we do plan on integrating comment registration into Movable Type Pro (which we’ll be talking about in more detail very soon), it’s an option that serves a different purpose than just blocking spam. If you want to prevent links to explicit pornography from appearing on your site, you shouldn’t have to be required to turn on comment registration.

Comments require approval before being posted When a comment is posted, you can receive an email that provides a clickable link you must visit before the comment can be posted on your site.

For webloggers with a small amount of readers, this solution may be ideal. However, if you receive a good deal of comments, it’s a solution that doesn’t scale. Additionally, it may ruin the spontaneity of discussion.

Image comprehension technology
Before a comment can be posted on a weblog, human eyes must enter a code that, ideally, is not readable by a computer.

This solution is not feasible because of accessibility issues. Additionally, spammers seem to be searching with bots and entering spam manually.

A possible solution for everyone?
The problem has intensified in the past couple of weeks, but the good news is that as more people have been hit by comment spam, actual solutions are beginning to emerge.

Specifically, Jay Allen’s MT-BlackList is a blacklist-based solution to comment spam for Movable Type weblogs. It checks the comment fields (body, URL, author, etc) for URLs commonly found in spam comments, and rejects the comment if it looks like spam. The core plugin is set to be released today (Monday), but one of its neatest features-in-development is the ability for weblog systems to share blacklist data using XML-RPC. This provides the basis of a collaborative system similar to Razor, with the option for more management over the items in your own system’s blacklist.

We’re deeply committed to finding a way to combat spammers and we’re determined to do it on a core system level so that everyone can take advantage of spam prevention. We’re working on integrating comment spam blocking for MT and TypePad, and the great thing about Jay’s solution is that it could be the start of a distributed spam blocking network for comments, an implementation of which could be included in multiple tools. But, like email, there isn’t one simple solution that can be switched on and end spam completely. Hopefully we’re moving a step closer.

What can you do to stop blog spamming? Below I have posted some methods that I have collected in the www. The layout is the following: first the description and second the links to the installation and documentation (always at the author´s website ? no copyright problems right?). I have tried to organize them starting from the easiest, GOOD LUCK!

1.Comment Spam Quick Fix from Burningbird’s. Easy method to start stoping spam in your blog. You add a hidden field to all of your comment forms and then MT look for that information when it processes the comment form. This simple process will eliminate most of bots spam comments (the most dangerous).

You only need to modify the following MT templates:
Individual data entry
Comment Listing Template
Comment Preview Template
Comment Error Page

2.Comment Queue Script/MT Hack from ScriptyGoddess. This script put all comments into a pending status until you approve or disapprove them. This solution may cause your blog a lost of interaction but you can target comments suspicious of spam. Some people will find this difficult because you must modify your MT installation and also you must watch your comments.

You can login into the script, see all the “pending” comments. Review/Edit/Delete the ones you don’t want on your blog. This method is indicated for blog owners who want to have their blogs open for anyone/everyone to join in on, but don’t like the idea of forcing registration before allowing comments from visitors.

3.Jacob’s “Edit/Delete Comment” notification. This solution requires some knowledge in MT perl files but is not very difficult. Jacob has modified the mt-comments.pm file adding a code to the bottom of the comments notification email that includes the link to the “Edit/Delete Comment” screen. This way you can delete easily all spam comments, is not the final solution but is recommended for moderate spam blogs (less than 10 spam comments/day).

4.Captcha Turing test to eliminate spam from bots. James Seng has developed a MT version of a Captcha Turing Test. This solution add a graphical validation code to your comment post form. The author must type the exact code (numbers) shown in a graphic in order for the comment to be valid. This eliminate all of the comment spam from bots. This method is used for big companies like Overture or Yahoo and nowadays is well implemented in internet online forms. Recomemended for blogs receiving spamming from bots.

5.James Seng Bayesian Filter for MT. Another great solution from James Seng. This plugin will allow you to train your MT to identify spam comments and trackback pings using Bayesian filtering technique which is hugely successful in fighting Email spams. The bayesian algorithm has been modified here to carter for the special characteristic of comments and pings. The system started off dumb but as you train the system, it will become better in identify spam. Once it is sufficient trained, it will require no or little maintenance.

6.Jay Allen’s comment Spam Blacklist. This plugin check urls in your comment form and trackbacks, then search it in a blacklist of known spammers, if found it doesn´t allow the comment to be processed. The main advantage of this method is that targets the core content of comment spam (url) and not the IP address or other easily changeable information. It is just as easy for someone to change their IP address using a proxy, or simply use a dialup account and reconnect to get a new one. The comments blacklisted never show up in the site and you can use also retroactive blacklistings to remove existing comment spam. The main drawback is that it doesn´t prevent from submission, just the display.

Other quick tips for a spam-free blog are:

a) Rename your comment script.

b) Don’t link to the comment script on your front page.

c) Separate “Preview” and “Post” into two separate scripts

Finally, the most effcient way to stop comment spam is to stop comments itself at your blog, but in my opinion then it wouldn´t be a blog. I know some webmasters that have made this, I invite them to allow comments again and use one of the methods of this page, don´t let spammers close your blog!